Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer who played a crucial role in establishing the field of
extragalactic astronomy and is generally regarded as one of the most important observational
cosmologists of the 20th century. Hubble is known for showing that the
recessional velocity of a galaxy increases with its distance from the earth, implying the universe is expanding, known as "
Hubble's law" although this relation had been discovered previously by
Georges Lemaître, who published his work in a less visible journal.